The present invention relates to the field of traumatology and orthopedics and more particularly has as its object a pin carrier clip intended for external bone fixation devices utilizing pins inserted into the bone. This is also referred to as a pin holder support.
By "traumatology" is understood casualty surgery and by "orthopedics" the correction of congenital malformations or malformations resulting from incorrectly aligned bone unions.
A number of devices permitting the transfer or displacement of a segment of a bone in relation to the remainder of the latter have been developed over a period of many years. Depending on circumstances the displacement required may be angular, longitudinal or rotational, or may comprise a combination of such displacements.
The devices used are mainly of two types: internal devices, which are introduced into the patient's body, and internal fixation means connected, by pins inserted into the bone, to the bone fragments requiring displacement or support.
These devices are always placed in position under anesthesia. In order to reduce the duration of the anesthesia to the minimum, it is endeavoured to develop devices which allow positioning at every possible angle, but which can easily be adjusted by a surgeon, who is not necessarily a mechanical expert.
The invention relates to the external fixation means connected to sets of pins inserted into each of the bone fragments which are to be positioned relative to each other, on each side of the fracture.
According to a first technique employed at the present time, hoop members are placed around the limb, the hoops being fastened on the one hand to pins or wires inserted into the bone and on the other hand to spacer bars between the hoops. Use is also made of frames disposed one on each side of the limb and connected by pins passing through the bone fragments.
According to another technique the pins are connected to a single fixation bar, which is disposed substantially parallel to the fractured bone. Each set of pins inserted into a bone fragment is clamped in a support, which is adapted to be oriented relative to the fixation bar and fixed to a fastening clip on said bar.
For the orientation of each set of pins, various systems of ball or universal joints are known, which have the disadvantage that their position cannot be continuously modified.
It has already been proposed to use parts having notched angular faces adapted to engage in corresponding parts, in relation to which they are fixed by connections means passing through a central bore, such as the system described in French Patent F-2,557,933. The articulation obtained with this system is however limited to the predetermined angular positions of the notches and in addition requires double adjustment, in two planes, in order to obtain the desired orientation, while furthermore the fastening of the pins is effected with an additional clamp system.
A pin carrier clip fastened to a curved guide member, as described in French Patent F-2,517,195, has also been proposed. The curved guide member is equipped with helical toothing intended for cooperation with a worm.
In addition, a device is also known which is composed of two members, one member being fastened to the pins and the other to the fixation bar, and one of them having a curved portion guiding the other, as described in American U.S. Pat. No. 4,628,922. This device requires the independent clamping of the pins and the locking in position of the members with the aid of independent clamp means.